## Precalculus (10th Edition)

We know that if a function is odd, then $f(-x)=-f(x).$ We know that if a function is eben, then $f(-x)=f(x).$ Hence we plug in $-x$ to see what happens. $f(-x)=\frac{4+(-x)^2}{1+(-x)^4}=\frac{4+x^2}{1+x^4}=f(x).$ Hence the function is even.